As is known, the cyclodextrins are cyclic, non reducible oligosaccharides containing 6, 7 or 8 glucopyranose units. They may be produced by enzymatic decomposition of starch. In the practice they are mainly used as a consequence of their ability to form inclusion complexes (Szejtli J.: Cyclodextrins and their Inclusion Complexes, Alkademiai Kiado, Budapest 1982). The reactivity of the primary and secondary alcoholic hydroxy groups on the rings of the six-member .alpha.-, the seven-member .beta.- and the eight-member .gamma.-cyclodextrin renders the preparation of derivatives having great molecular mass (cyclodextrin polymers) possible.
According to the literature cyclodextrin polymers, which are water soluble, and those, which are water insoluble but swell in water, are known. Due to the greater molecular mass and cross-linked structure the latters are not soluble in any solvent.
Water soluble cyclodextrin polymer may be obtained in two way: unsaturated monomer is prepared from cyclodextrin and this will be polymerized (J. Polym.Sci.Lett. 13, 357 (1975)) or the cyclodextrin is cross-linked with a suitable bifunctional reagent, preferably diepoxy derivative or epichlorohydrin (GB patent specification No. 1,244,990 and Hungarian patent specification No. 180,597).
By both processes products having medium molecular mass may be obtained which may be dissolved in water well and form inclusion complex. The stability of their complexes is generally greater than that of the monomer cyclodextrins. This may be explained by the advantageous steric position of the rings connected each other and in case of .beta.-cyclodextrin by the greater solubility of the polymer (Macromolecules 2, 705 (1976), Proceedings of I. Int. Symp. on Cyclodextrins (1981) 345).
With the known cyclodextrin polymers mentioned above complexes may be produced in many fields, practically in all cases when the molecule to be included, i.e. the so-called "guess molecule" is a neutral group. While complexing salts problems may exist due to the ionic character of the salts. So a cyclodextrin polymer would be advantageous which contains both the acidic and basic substituents capable of forming salts and the cyclodextrin rings capable of forming inclusion complexes. In the literature no such solution is, however, described where the two above mentioned functional units would form a part of a molecule having high molecular weight. Cyclodextrin derivatives, in which the cyclodextrin rings are substituted by several groups capable of forming salts, e.g. carboxyalkyl, sulfoalkyl or aminoalkyl groups, are known (Starke, 23, 134 (1971), U.S. Pat. No. 3,553,191). These substituted cyclodextrins are not more advantageous than the unsubstituted cyclodextrins since they have relatively low molecular weights.